1. Field of the Invention
The present invention relates to the production of superconductor materials.
2. Description of the Prior Art
It is known to this art that, in theory, when superconductors are cooled to very low temperatures, they offer no resistance to the flow of an electric current.
Until somewhat recently, the state of superconductivity was observed only in certain materials below a threshold temperature, designated the "critical temperature", such threshold typically approximating absolute zero. This type of limitation obviously presents a serious drawback in the large scale development of any potential practical application resulting from superconductivity.
Very recently, however, research has given rise to the development of new materials having superconducting properties at higher temperatures, i.e., temperatures on the order of from 70.degree. to 90.degree. K., or even as high as 100.degree. K.
These materials are principally based on the rare earths, alkaline earths, transition metals and oxygen. More specifically, the most promising systems studied appear to be those based on yttrium and/or lanthanum, barium and/or strontium and/or calcium, copper and/or nickel and/or cobalt and/or manganese, and oxygen.
The mode of synthesis generally described in the literature for producing such materials entails a solid phase reaction at elevated temperatures (1,000.degree. C.) between oxides and/or salts containing a volatile anion (for example, the carbonate) of the corresponding elements, with the latter compounds being present in the form of powders.
However, this process has the disadvantage of requiring delicate controls and the powders constituting the final product are largely inadequate in terms of their sinterability.
But, relative to certain practical applications, only the use of sintered superconducting products is of any real interest.
Therefore, it is essential that dense and homogeneous sintered materials be available which retain the intrinsic superconducting characteristics of the initial powders. Consequently, it is necessary to first have homogeneous superconducting powders that are readily and easily sintered.